Multiplexer for tap controller and WSP controller outputs

ABSTRACT

In a first embodiment a TAP  318  of IEEE standard 1149.1 is allowed to commandeer control from a WSP  202  of IEEE standard P1500 such that the P1500 architecture, normally controlled by the WSP, is rendered controllable by the TAP. In a second embodiment (1) the TAP and WSP based architectures are merged together such that the sharing of the previously described architectural elements are possible, and (2) the TAP and WSP test interfaces are merged into a single optimized test interface that is operable to perform all operations of each separate test interface.

This application is a divisional of prior application Ser. No.12/791,133, filed Jun. 1, 2010, currently pending now U.S. Pat. No.8,078,927, issued Dec. 13, 2011;

Which is a divisional of prior application Ser. No. 12/165,928, filedJul. 1, 2008, now abandoned; Which was a divisional of prior applicationSer. No. 10/874,054, filed Jun. 21, 2004, now U.S. Pat. No. 7,409,611,granted Aug. 5, 2008; Which claims priority under USC 119(e) (1) ofProvisional Application No. 60/483,437, filed Jun. 27, 2003.

RELATED PATENTS/APPLICATIONS

This application is related to pending patent publication US2001/0037479 A1, which is incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to integrated circuit design andtesting, and in particular to an improved test interface andarchitecture that may be included in intellectual property core circuitsand integrated circuits.

BACKGROUND OF THE INVENTION

Today large system-on-chips (SOC) are being designed that include amyriad of different types of complex functional circuits. StandardizedIC test interfaces and architectures are needed for testing thesefunctional circuits within the IC, and also for testing theboard/substrate on which the IC will eventually reside.

This disclosure describes two separate IC test standards, IEEE 1149.1and IEEE P1500, that can be used to test circuitry embedded within ICs.Each IC test standard has its own test interface and architecture, andunique testing features. Thus an IC may require both test standards tobe implemented to achieve an overall testing goal. Having to includeboth test standards in ICs can be costly in circuit area overhead andtest complexity.

To facilitate the understanding of the present invention, an overview oftwo test standards to be combined is provided. FIGS. 1-17 give anoverview of IEEE standard 1149.1 and FIGS. 18-45 give an overview ofIEEE standard P1500.

IEEE 1149.1 Overview

FIG. 1 illustrates an example of a test interface 104 and architecture102 that is commonly used in both ICs and core circuits within ICs. Thetest interface and architecture are well known and were standardized in1990 as IEEE Standard 1149.1. While initially developed as an IC teststandard for primarily supporting board level IC to IC interconnecttesting, this standard has evolved into additional uses and formed thebasis for a family of additional IEEE standards.

The test interface 104 includes a test access port (TAP) state machinecontroller and signals TDI, TCK, TMS, TRST, and TDO. The testarchitecture 102 includes an instruction register and a set ofselectable data registers. As seen in FIG. 1, the data registersconsists of various types including but not limited too, a boundary scanregister, digital test registers, debug/emulation registers, programmingregisters, mixed signal test registers, and a bypass register. The TAPreceives a test clock (TCK), test mode select (TMS), and test reset(TRST) input signals. The TAP responds to the TCK and TMS input signalsto shift data through either the instruction register or a selected dataregister from the test data input (TDO) signal to the test data output(TDO) signal. The TAP has proven to be an efficient and popular testcontrol interface for ICs and cores.

For example, other TAP based standards have evolved from the originalIEEE 1149.1 standard. These other TAP based standards include; (1) IEEEstandard 1149.4 (a mixed signal test standard), (2) IEEE standard 1149.6(an advanced interconnect test standard), (3) IEEE standard 1532 (anin-system programming standard), and (4) IEEE standard 5001 (adebug/emulation standard). The naming of the data registers in FIG. 1indicates the presence of these additional TAP based IEEE standards. Inaddition to the multiplicity of TAP based IEEE standards, numerous coreand/or IC provider companies have developed proprietary emulation anddebug architectures based upon the IEEE 1149.1 TAP and architecture ofFIG. 1.

FIG. 2 is a different view of the FIG. 1 test interface and architectureemphasizing the instruction registers ability to select one of the dataregisters for access between TDI and TDO.

FIG. 3 is a block diagram of the key circuit elements of FIGS. 1 and 2.The TAP 318 regulates TDI to TDO access of the instruction register 314via instruction register control bus 302 and the TDI to TDO access of aselected one of a set of data registers 316 via data register controlbus 304. As seen, a gating circuit 308 receives input 306 from theinstruction register to allow the data register control bus 304 from theTAP to pass through the gating circuit and be output on bus 310 tooperate a selected data register. The gating circuit is typically viewedas being part of the instruction register and is shown in FIG. 2 as thedotted box on the instruction register. The data registers 316 alsoreceive mode control input 312 from the instruction register to placethem in various modes of operation.

FIG. 4 indicates the TAP's state controller diagram. The TAP is clocked,via TCK, through these states in response to input on TMS. Since allTAPs operate from this diagram, standardized plug and play compatibilitybetween TAPs is guaranteed. The operation of the TAP controller is wellknown.

FIG. 5 illustrates typical TAP 318 input (TCK, TMS, TRST) and outputsignals. The ClockIR, ShiftIR, and UpdateIR form the signals on bus 302to the instruction register. The ClockDR, ShiftDR, and UpdateDR form thesignals on bus 304 to gating circuit 308. The Select signal is used toselect either the instruction register or selected data register to becoupled to TDO. The Reset signal is used to reset the instructionregister and optionally the data registers whenever the TAP is in theTRST state of FIG. 4. As seen in FIG. 5, a TAP state bus 502 can beoutput from the TAP to indicate what state of FIG. 4 the TAP is in. TheTAP state bus is useful in controlling synchronous instruction and dataregister designs and is therefore shown as being part of the instructionand data control buses 302 and 304, respectively.

FIG. 6 illustrates a gated instruction register design style. Theinstruction register comprises a shift register 602, an update register604, and an instruction decode logic 606. The shift register comprisesserially connected scan cells 608 that operate to capture and shift datafrom TDI to TDO. The update register comprises a flip-flop or latch 610for each shift register scan cell 608. In operation, the TAP outputscontrol (ClockIR and ShiftIR) to cause the shift register to capturedata (IN) then shift data from TDI to TDO. After capturing and shifting,the TAP outputs control (UpdateIR) to cause the latches 610 of updateregister 604 to load data from the scan cells 608. The latched data isoutput from the update register to the decode logic, where it is decodedinto control output bus 612 which, among other things, drives buses 306and 312. While not shown, both the scan cell 608 and update latch 610can be reset by the reset output from the TAP.

FIG. 7 illustrates a timing example of the TAP performing the abovedescribed gated instruction register scan operation. As seen, the TAPgates the ClockIR on in the CaptureIR state to perform the captureoperation (C) and in the ShiftIR state to perform the shift operations(S). The TAP manipulates the ShiftIR output to control the scan cells608 to perform the capture and shift operations. Also, the TAP gates aclock pulse on UpdateIR during the UpdateIR state to perform the updateoperation (U).

FIG. 8 illustrates a synchronous instruction register design style. Thesynchronous instruction register design style differs from the gatedinstruction design style in that the shift register 802 is comprised ofscan cells 804 which operate from the free running TCK input, not theClockIR input of FIG. 6. The shift register 802 receives TAP state (502)input from bus 302 to indicate when the TAP is in the CaptureIR stateand ShiftIR state. When the TAP is in the CaptureIR state the scan cells804 capture data (IN) and when the TAP is in the ShiftIR state the scancells shift data from TDI to TDO. When the TAP is not in the CaptureIRor ShiftIR state, the scan cells hold their present value. The operationof the update register 604 and decode logic 606 is the same as describein FIG. 6.

FIG. 9 illustrates a timing example of the TAP performing the abovedescribed synchronous instruction register scan operation. As seen, whenthe TAP enters the CaptureIR state the scan cells 804 perform a captureoperation (C) and when the TAP enters the ShiftIR state the scan cellsperform shift operations (S). As with the FIG. 8 timing diagram, the TAPgates a clock pulse on UpdateIR during the UpdateIR state to perform theupdate operation (U).

FIG. 10 illustrates a first gated data register design style. The dataregister 1002, referred to as data register 1, is an example of a gatedboundary scan data register that could be used at the I/O boundary of acore or IC. Data register 1 comprises serially connected boundary scancells 1004 each having an scan cell 1006 operable to capture data fromthe IN input and to shift data from TDI to TDO, and an update latch 1008operable to load data from the scan cell. If selected by the instructionin the instruction register, gates 1010-1012 within gating circuit 308are enabled by a signal 1014 on bus 306 to couple the TAP's ClockDR,ShiftDR, and UpdateDR outputs to data register 1's Clock-1, Shift-1, andUpdate-1 inputs, respectively. This enables scan access of data register1. In this and all following Figures, a capital “A” in a gate symbolindicates the gate is an AND function and a capital “O” in a gate symbolindicates the gate is an OR function. During a data scan operation, theTAP outputs control (ClockDR and ShiftDR) to cause the scan cells 1006of boundary scan cells 1004 to capture data (IN) then shift data fromTDI to TDO. After capturing and shifting, the TAP outputs control(UpdateDR) to cause the update latches 1008 of the boundary scan cellsto load data from the scan cells 1006. If data register 1 is in testmode, the Mode-1 input from instruction register bus 312 will be set tocause the data in update latch 1008 to be output from data register1002.

FIG. 11 illustrates a timing example of the TAP performing the abovedescribed gated data register scan operation. As seen, the TAP gatesClock-1 (ClockDR) on in the CaptureDR state to perform the captureoperation (C) and in the ShiftDR state to perform the shift operations(S). The TAP manipulates Shift-1 (ShiftDR) to control the scan cells1006 to perform capture and shift operations. Also, the TAP gates aclock pulse on UpdateDR-1 during the UpdateDR state to perform theupdate operation (U). It is important to note for later reference inthis and following timing Figures that the dotted box area beginningwith A and ending with B indicates when the TAP is in the ShiftDR state.

FIG. 12 illustrates a first synchronous data register design style. Thedata register 1202, referred to as data register 2, is an example of asynchronous boundary scan data register that could be used at the I/Oboundary of a core or IC. Data register 2 comprises serially connectedboundary scan cells 1204 each having an scan cell 1206 operable tocapture data from the IN input and to shift data from TDI to TDO, and anupdate latch 1208 operable to load data from the scan cell. If selectedby the instruction in the instruction register, gates 1210-1214 withingating circuit 308 will be enabled by a signal 1216 on bus 306 to couplethe TAP's CaptureDR state, ShiftDR state, and UpdateDR outputs to dataregister 2's Capture-2, Shift-2, and Update-2 inputs, respectively. Thisenables scan access of data register 2. The Clock-2 input of dataregister 2 is coupled to the free running TCK. During a data scanoperation, the TAP outputs state indications (bus 502 & 304) to causethe scan cells 1206 to capture data (IN) during the CaptureDR state(Capture-2 set high) then shift data from TDI to TDO during the ShiftDRstate (Shift-2 set high). As seen, the scan cell holds its state whenthe TAP is not in the CaptureDR or ShiftDR states. After capturing andshifting, the TAP outputs control (UpdateDR) to cause the update latches1208 of the boundary scan cells to load data from the scan cells 1206.If data register 2 is in test mode, the Mode-2 input from instructionregister bus 312 will be set to cause the data in update latch 1208 tobe output from data register 1202.

FIG. 13 illustrates a timing example of the TAP performing the abovedescribed synchronous data register scan operation. As seen, when theTAP is in the CaptureDR state, the Capture-2 input is high causing dataregister 2 to capture data (C). When the TAP is in the ShiftDR state theShift-2 input is high causing data register 2 to shift data (S). Also,the TAP gates a clock pulse on UpdateDR-2 during the UpdateDR state toperform the update operation (U).

FIG. 14 illustrates a second gated data register design style. The dataregister 1402, referred to as data register 3, is an example of a gatedscan data register that could be used as an internal scan path of a coreor IC. Data register 3 comprises serially connected conventional scancells 1404 each operable to capture data from the IN input and to shiftdata from TDI to TDO. If selected by the instruction in the instructionregister, multiplexers 1404-1406 within gating circuit 308 are enabledby a signal 1408 on bus 306 to couple the TAP's ClockDR and ShiftDRoutputs to data register 3's Clock-3 and Shift-3 inputs, respectively.Multiplexers 1404-1406 are used instead of gates since switching betweena functional and test clocks and between functional and test modes isrequired when using scan cells that are shared for functional and testoperations. This enables scan access of data register 3. During a datascan operation, the TAP outputs control (ClockDR and ShiftDR) to causethe scan cells 1404 to capture data (IN) then shift data from TDI toTDO.

FIG. 15 illustrates a timing example of the TAP performing the abovedescribed gated data register scan operation. As seen, the TAP gatesClock-3 (ClockDR) on in the CaptureDR state to perform the captureoperation (C) and in the ShiftDR state to perform the shift operations(S). The TAP manipulates Shift-3 (ShiftDR) to control the scan cells1404 to perform capture and shift operations.

FIG. 16 illustrates a second synchronous data register design style. Thedata register 1602, referred to as data register 4, is an example of asynchronous scan data register that could be used as an internal scanpath of a core or IC. Data register 4 comprises serially connected scancells 1604 each operable to capture data from the IN input and to shiftdata from TDI to TDO. If selected by the instruction in the instructionregister, multiplexers 1606-1610 within gating circuit 308 will beenabled by a signal 1612 on bus 306 to couple the TAP's CaptureDR stateoutput, the TAP's ShiftDR state output, and the TCK to data register 4'sCapture-4, Shift-4, and Clock-4 inputs, respectively. Again,multiplexers 1606-1610 are used instead of gates since switching betweena functional and test clocks and between functional and test modes isrequired when using scan cells that are shared for functional and testoperations. This enables scan access of data register 4. During a datascan operation, the TAP outputs state indications to cause the scancells 1604 to capture data (IN) during the CaptureDR state (Capture-4set high) then shift data from TDI to TDO during the ShiftDR state(Shift-4 set high). As seen, the scan cell holds its state when the TAPis not in the CaptureDR or ShiftDR states.

FIG. 17 illustrates a timing example of the TAP performing the abovedescribed synchronous data register scan operation. As seen, when theTAP is in the CaptureDR state, the Capture-4 input is high causing dataregister 4 to capture data (C). When the TAP is in the ShiftDR state theShift-4 input is high causing data register 4 to shift data (S).

IEEE P1500 Overview

FIG. 18 illustrates an example of a test interface 1804 and architecture1802 that is being developed as IEEE standard P1500. This standard testinterface and architecture is being developed for the purpose of testingcores within ICs. While not yet standardized, the state of the P1500standard is stable and near complete. The architectural similaritiesbetween the IEEE P1500 standard of FIG. 18 and the previously describedIEEE 1149.1 standard of FIG. 1 are clearly seen.

The test interface 1804 includes a wrapper serial port (WSP) and signalsWSI, Clock, Capture, Shift, Update, Transfer, Select, Reset, and WSO.The architecture 1802 includes a wrapper instruction register and a setof selectable wrapper data registers. As seen in FIG. 18, the wrapperdata registers consists of a wrapper boundary scan register, digitaltest registers, and a wrapper bypass register. The WSP receives clock,capture, shift, update, transfer, select, and reset input signals. TheWSP responds to these signals to shift data through either the wrapperinstruction register or a selected wrapper data register from thewrapper serial input (WSI) signal to the wrapper serial output (WSO)signal. Unlike the TAP of FIG. 1, which is a state machine, the WSP issimply a combinational decode circuit. With the exception that IEEEstandard P1500 uses a WSP in the test interface 1804 and IEEE standard1149.1 uses a TAP in the test interface 104, the two standards are verysimilar architecturally. For the purpose of simplifying the followingdescription, it will be assumed that the IEEE P1500 architecture 1802can be viewed as being the same as the previously described IEEE 1149.1architecture 102 of FIG. 1. While there may be subtle differencesbetween the two architectures, these differences are transparent to theoverall objective of the present invention.

FIG. 19 is a different view of the FIG. 18 test interface andarchitecture emphasizing the instruction registers ability to select oneof the data registers for access between WSI and WSO.

FIG. 20 is a block diagram of the key circuit elements of FIGS. 18 and19. The WSP 202 regulates WSI to WSO shifting of the instructionregister 314 via instruction register control bus 302 and the WSI to WSOshifting of a selected data within a set of data registers 316 via dataregister control bus 304. As seen, a gating circuit 308 receives input306 from the instruction register to allow the data register control bus304 from the WSP to pass through the gating circuit and be output on bus310 to operate the selected data register. The gating circuit istypically viewed as being part of the instruction register and is shownin FIG. 18 as the dotted box on the instruction register. The dataregisters 316 also receive mode control input 312 from the instructionregister to place them in various modes of operation.

FIG. 21 illustrates an example WSP 202 circuit. As mentioned, the WSP isa combinational circuit and does not include any sequential memoryelements. Like the TAP, the WSP has a control bus 302 of outputs,ClockIR, ShiftIR, CaptureIR, and UpdateIR, that are used to controlscanning of the instruction register, and a control bus 304 of outputs,ClockDR, ShiftDR, CaptureDR, UpdateDR, and TransferDR, that are used tocontrol scanning of a selected data register.

The operation of the WSP is simple. If the select input to the WSP islow the select output from the WSP is low and the WSP couples the clock,shift, capture, update, and transfer inputs to the ClockDR, ShiftDR,CaptureDR, UpdateDR, and TransferDR outputs to enable scanning of a dataregister. The low on the select output selects the data register betweenWSI and WSO. If the select input to the WSP is high the select outputfrom the WSP is high and the WSP couples the clock, shift, capture, andupdate inputs to the ClockIR, ShiftIR, CaptureIR, and UpdateIR outputsto enable scanning of the instruction register. The high on the selectoutput selects the instruction register between WSI and WSO. The resetoutput from the WSP is coupled to the reset input to the WSP and isused, as was the reset output of the TAP in FIG. 5, to reset theinstruction register and optionally the data registers when assertedlow. The WSP Transfer input and TransferDR output signals are new dataregister control signals introduced by IEEE P1500. An example of theiruse will be described later in regard to FIGS. 40-45.

FIGS. 22 and 23 are provided to illustrate that the WSP is capable ofproviding timing and control to the gated instruction register design ofFIG. 6. FIG. 23 illustrates that the WSP can mimic the gated TAP timingdiagram of FIG. 7. The dotted line clock pulses shown on portions of theinactive clock input signal indicates TCKs that would be input to theTAP during the instruction register scan timing diagram of FIG. 7.

FIGS. 24 and 25 are provided to illustrate that the WSP is capable ofproviding timing and control to the synchronous instruction registerdesign of FIG. 8. FIG. 25 illustrates that the WSP can mimic thesynchronous TAP timing diagram of FIG. 9. Being able to mimic TAPinstruction and, as will be shown below, data register scan timing isimportant since it allows for serially connecting the IEEE 1149.1 andIEEE P1500 standard test architectures together in a daisy-chainarrangement.

FIGS. 26 and 27 are provided to illustrate that the WSP is capable ofproviding timing and control to the gated data register 1 design of FIG.10. FIG. 27 illustrates that the WSP can mimic the gated TAP timingdiagram of FIG. 11. Again, the dotted line clock pulses shown onportions of the inactive clock input signal indicates TCKs that would beinput to the TAP during the data register scan timing diagram of FIG.11.

FIG. 28 illustrates an alternate method of scanning gated data register1 of FIG. 26. Since the WSP is combinational in operation it does nothave to mimic TAP state transition timing. Indeed one of the primaryreasons IEEE P1500 uses the WSP instead of the TAP is that the WSPallows greater flexibility in controlling scan operations. For example,in FIG. 28 the WSP provides scan timing control to data register 1 wherethe shift (S), capture (C), and update (U) operations are occurring in atightly timed sequence.

FIGS. 29 and 30 are provided to illustrate that the WSP is capable ofproviding timing and control to the synchronous data register 2 designof FIG. 12. FIG. 31 illustrates that the WSP can mimic the synchronousTAP timing diagram of FIG. 13.

FIG. 31 illustrates an alternate method of scanning synchronous dataregister 2 of FIG. 26, whereby the shift (S), capture (C), and update(U) operations are occurring in a tightly timed sequence.

FIGS. 32 and 33 are provided to illustrate that the WSP is capable ofproviding timing and control to the gated data register 3 design of FIG.14. FIG. 33 illustrates that the WSP can mimic the gated TAP timingdiagram of FIG. 15.

FIGS. 34 and 35 illustrate alternate methods of scanning gated dataregister 3 of FIG. 32. FIG. 34 illustrates a tightly timed capture (C)and shift (S) scanning sequence, and FIG. 35 illustrates a tightly timedback to back capture (C) and shift (S) sequence.

FIGS. 36 and 37 are provided to illustrate that the WSP is capable ofproviding timing and control to the synchronous data register 4 designof FIG. 16. FIG. 37 illustrates that the WSP can mimic the synchronousTAP timing diagram of FIG. 17.

FIGS. 38 and 39 illustrate alternate methods of scanning synchronousdata register 4 of FIG. 36. FIG. 38 illustrates a tightly timed capture(C) and shift (S) scanning sequence, and FIG. 39 illustrates a tightlytimed back to back capture (C) and shift (S) sequence.

FIG. 40 illustrates one example of how the IEEE P1500 Transfer signalmight be used during test. Data register 5, 4002, is comprised of aplurality of serially connected scan cells 4004, each capable ofperforming shift and transfer operations. As seen, the scan cell 4004circuit example consists of an input multiplexer 4012, a series of flipflops 4014, and an output multiplexer 4016. The input multiplexer 4012serves to either shift data from TDI (WSI) to TDO (WSO) in shift mode(Shift5 is high) or to shift in data from the output (OUT) of the outputmultiplexer 4016 during transfer mode (Transfer5 is high). Gates 4006and 4008 of gating circuit 308 are enabled by signal 4010 to couple theClockDR and TransferDR outputs from the WSP to the Clock-5 andTransfer-5 inputs to data register 5, respectively, when a transferinstruction is loaded into the instruction register.

As seen in FIG. 40, a pair of Mode-5 signals, Mode-5 a and 5 b, areoutput from the instruction register on bus 312 to control the scan celloutput multiplexers 4016. During transfer operations, the outputmultiplexers 4016 of scan cells 4004 that output test signals will becontrolled to couple the output of the flip flops 4014 to the outputmultiplexer output (OUT), while the output multiplexers 4016 of scancells 4004 that input test signals will be controlled to couple theinput (IN) of the scan cell to the output (OUT) of output multiplexers4016. Thus two separately controllable Mode-5 signals, Mode-5 a and 5 b,will typically be required from the instruction register to achieve adesired output multiplexer test setting.

FIG. 41 illustrates an example transfer test arrangement whereby an ANDgate function 4102 to be tested is bounded by two cells A and B 4004 forproviding input to the AND gate and one cell C 4004 for receiving outputfrom the AND gate. The AND gate can exist within a core containing theIEEE P1500 architecture or external to a core containing the IEEE P1500architecture. Also, the cells A-C may be in the same data register 5 ofone IEEE P1500 architecture or be in separate data register 5's ofseparate IEEE P1500 architectures. The dotted line beginning at the TDIinput of cell A and ending at the TDO output of cell C indicates theprocess of shifting data through the cells to load test input data tocells A and B and unload test output data from cell C. As seen, theshifting occurs in response to Shift-5 being high, Transfer-5 being low,and Clock-5 being active. While for simplicity the example of FIG. 41shows the serial path to only include cells A-C, additional scan cellsof various types may exist in the scan path as well.

FIG. 42 illustrates cells A, B, and C 4004 in their transfer mode. Asseen, the transfer mode occurs in response to Shift-5 being low,Transfer-5 being high, and Clock-5 being active. During transfer mode,cells A and B circulate their data, as shown in dotted line, from theoutput (OUT) of their output multiplexers to the input of their inputmultiplexers, to provide the test signal input to AND gate 4102.Simultaneously, cell C shifts in the test signal output from AND gate4102, again as shown in dotted line. The Mode-5 a and Mode-5 b inputs tothe cell output multiplexers have been set, as previously described, forthis particular transfer test arrangement.

FIG. 43 shows a first transfer test input and output session to AND gatefunction 4102. FIG. 44 shows a second transfer test input and outputsession to AND gate function 4102. The first transfer test session teststhe AND gate's ability to pass a stream of data from its In1 input toits Out output, while its In2 input is high. The second transfer testsession tests the AND gate's ability to pass a stream of data from itsIn2 input to its Out output, while its In1 input is high.

FIG. 45 illustrates an example timing diagram for the transfer test ofthe test arrangement of FIGS. 41-44. Firstly, the cells A-C are shifted,during time frame 4502, to load the test input patterns to be appliedduring the first transfer test session of FIG. 43. Secondly, the firsttransfer test session of FIG. 43 is executed during time frame 4504.Thirdly, the cells A-C are shifted, during time frame 4506 to load thetest input patterns to be applied during the second transfer testsession of FIG. 44 and to unload the results of the first transfer testsession of FIG. 43. Fourthly, the second transfer session of FIG. 44 isexecuted during time frame 4508. Lastly, the cells A-C are shifted,during time frame 4510 to unload the test results of the second transfertest session.

While the above description has provided one detailed example of how anIEEE P1500 transfer test may be performed, there are numerous other waysof designing and operating scan cells to achieve transfer testing.

FIG. 46 represents the problems the present invention anticipates ifboth TAP based (i.e. IEEE 1149.1, 1149.4, 1149.6, 1532, 5000, andad-hoc) and the WSP based (i.e. IEEE P1500) standard architectures(domains) are required in core and/or IC designs. In FIG. 46, box 4602represents a circuit which can be either a core circuit for use in an ICor an entire IC. The circuit 4602 is shown including both TAP basedstandards (1149.1, 1149.4, 1149.6, 1532, 5000, and/or ad-hoc) and theWSP based standard (IEEE P1500).

As seen in FIG. 46, each of the TAP based standards included in circuit4602 advantageously share a common TAP 318 interface and architecture4604. The architecture 4604 includes a commonly shared instructionregister 314, a commonly shared set of selectable data registers 316,commonly shared gating circuitry 308, and commonly shared instruction302 and data 304 control buses to the commonly shared TAP 318. Theexternal TAP test bus 4608 is achieved using 5 signals (TDI, TDO, TCK,TMS, and TRST). Regardless of whether circuit 4602 is a core or an IC,these 5 signals are dedicated and reserved for use in accessing the TAPto perform testing or other operations with the common architecture4604. The availability of the dedicated TAP test bus has proven verybeneficial since it allows non-intrusive access to a functionallyoperating circuit 4602 to perform real time test, emulation, debug, andother operations. The dedicated TAP test bus has also lead to an everincreasing set of TAP interface support tools supporting test,emulation, debug, programming, and other TAP based operations.

As seen in FIG. 46, the IEEE P1500 WSP 202 interface and architecture4610 is separate from the IEEE 1149.1 TAP 318 interface and architecture4604. Therefore the IEEE P1500 architecture is forced to include its owninstruction register 314, its own set of selectable data registers 316,its own gating circuitry 308, and its own instruction 302 and data 304control buses to WSP 202. The primary reason for this forced separationis due to the differences in operation between the TAP 318 and WSP 202interfaces. The external test bus 4612 to WSP 202 is achieved using 9signals (WSI, WSO, Clock, Capture, Shift, Update, Transfer, Select, andReset). If circuit 4602 is a core, these 9 signals will be dedicatedterminals of the core. However, if circuit 4602 is an IC, these 9signals are not required to be dedicated ICs pins, as are the TAP pins4608, and will typically be shared with functional pins on the IC andinvoked only when testing of the IC is required. If they are shared itis not possible to use them for real time test, emulation, debug, orother operations that can be used with the TAP 318 and its dedicatedtest bus 4608. The non-dedicated nature of the WSP test bus 4612 willmost likely limit use of IEEE P1500 in other areas such as emulation anddebug. However, since improved testing of core based ICs is the primaryobjective of IEEE P1500 that limitation will not matter, especiallysince TAP based solutions already exist for these expanded needs.

If the circuit 4602 is a core for use in an IC it will require a 5signal bus for interfacing to the TAP 318 and a 9 signal bus forinterfacing to the WSP 212. The total number of signals therefore thatneed to be routed in the IC for connection to core 4602 is 14. In someICs the routing of 14 test signals to a core can be prohibitive,especially if multiple cores exist with each potentially needing its ownbus of 14 test signals. Thus having two separate standards implementedin a core, each with separate test bus interfaces, can lead to problemsrelated to wire routing area overhead.

From the above description it is clear that if TAP based and WSP baseddomains are used in a circuit 4602, the area overhead will be increaseddue to the need of the WSP domain to have its own architecture separatefrom the TAP domain architecture. Also it is clear that access to WSPdomains, unlike TAP domains, will be limited to testing circuits 4602when circuits 4602 are in a non-functional mode of operation. Further,it is clear that due to the nature of the non-dedicated WSP 9 pininterface, the range of WSP interface support will be most likelylimited to testing. Lastly, having both TAP and WSP based domains incores can lead to IC wire routing and density problems.

SUMMARY OF THE INVENTION

This disclosure describes methods of partially or completely combiningthe two test standards together such that an IC need only include onetest standard instead of two test standards.

In accordance with the present invention, first and second embodimentsare provided to remedy the described problems of having two separatestandards implemented in cores and/or ICs. The first embodiment is anapproach whereby a TAP 318 is allowed to commandeer control from the WSP202 such that the P1500 architecture, normally controlled by the WSP, isrendered controllable by the TAP. The second embodiment is an approachwhereby; (1) the TAP and WSP based architectures are merged togethersuch that the sharing of the previously described architectural elementsare possible, and (2) the TAP and WSP test interfaces are merged into asingle optimized test interface that is operable to perform alloperations of each separate test interface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates IEEE standard 1149.1.

FIG. 2 illustrates a simplified view of IEEE standard 1149.1.

FIG. 3 illustrates circuit blocks of IEEE standard 1149.1.

FIG. 4 illustrates the state diagram of the IEEE 1149.1 TAP statemachine.

FIG. 5 illustrates an IEEE 1149.1 TAP state machine in more detail.

FIG. 6 illustrates a IEEE 1149.1 gated instruction register designstyle.

FIG. 7 illustrates a TAP gated instruction register timing diagram.

FIG. 8 illustrates a IEEE 1149.1 synchronous instruction register designstyle.

FIG. 9 illustrates a TAP synchronous instruction register timingdiagram.

FIG. 10 illustrates an IEEE 1149.1 data register 1 design style.

FIG. 11 illustrates a TAP data register 1 timing diagram.

FIG. 12 illustrates an IEEE 1149.1 data register 2 design style.

FIG. 13 illustrates a TAP data register 2 timing diagram.

FIG. 14 illustrates an IEEE 1149.1 data register 3 design style.

FIG. 15 illustrates a TAP data register 3 timing diagram.

FIG. 16 illustrates an IEEE 1149.1 data register 4 design style.

FIG. 17 illustrates a TAP data register 4 timing diagram.

FIG. 18 illustrates IEEE standard P1500.

FIG. 19 illustrates a simplified view of IEEE standard P1500.

FIG. 20 illustrates circuit blocks of IEEE standard P1500.

FIG. 21 illustrates an IEEE P1500 WSP in more detail.

FIG. 22 illustrates the WSP accessing the gated instruction register.

FIG. 23 illustrates a WSP gated instruction register timing diagram.

FIG. 24 illustrates a WSP accessing the synchronous instructionregister.

FIG. 25 illustrates a WSP synchronous instruction register timingdiagram.

FIG. 26 illustrates a WSP accessing data register 1.

FIG. 27 illustrates a first WSP data register 1 timing diagram.

FIG. 28 illustrates a second WSP data register 1 timing diagram.

FIG. 29 illustrates a WSP accessing data register 2.

FIG. 30 illustrates a first WSP data register 2 timing diagram.

FIG. 31 illustrates a second WSP data register 2 timing diagram.

FIG. 32 illustrates a WSP accessing data register 3.

FIG. 33 illustrates a first WSP data register 3 timing diagram.

FIG. 34 illustrates a second WSP data register 3 timing diagram.

FIG. 35 illustrates a third WSP data register 3 timing diagram.

FIG. 36 illustrates a WSP accessing data register 4.

FIG. 37 illustrates a first WSP data register 4 timing diagram.

FIG. 38 illustrates a second WSP data register 4 timing diagram.

FIG. 39 illustrates a third WSP data register 4 timing diagram.

FIG. 40 illustrates a WSP accessing a data register 5 design style.

FIG. 41 illustrates the shift mode of scan cells in data register 5.

FIG. 42 illustrates the transfer mode of scan cells in data register 5.

FIG. 43 illustrates the first transfer operation of data register 5 scancells.

FIG. 44 illustrates the second transfer operation of data register 5scan cells.

FIG. 45 illustrates a data register 5 shift and transfer timing diagram.

FIG. 46 illustrates a circuit including both IEEE 1149.1 and P1500standards.

FIG. 47 illustrates the circuit of FIG. 46 implementing the firstembodiment.

FIG. 48 illustrates the TAP and WSP control output multiplexer of FIG.46.

FIG. 49 illustrates the circuit of FIG. 46 implementing the secondembodiment.

FIG. 50 illustrates the test interface and architecture of the secondembodiment.

FIG. 51 illustrates the circuit blocks of the second embodiment.

FIG. 52 illustrates the second embodiment accessing data register 1.

FIG. 53 illustrates a data register 1 timing diagram of the secondembodiment.

FIG. 54 illustrates the second embodiment accessing data register 2.

FIG. 55 illustrates a data register 2 timing diagram of the secondembodiment.

FIG. 56 illustrates the second embodiment accessing data register 3.

FIG. 57 illustrates a first data register 3 timing diagram of the secondembodiment.

FIG. 58 illustrates a second data register 3 timing diagram of thesecond embodiment.

FIG. 59 illustrates the second embodiment accessing data register 4.

FIG. 60 illustrates a first data register 4 timing diagram of the secondembodiment.

FIG. 61 illustrates a second data register 4 timing diagram of thesecond embodiment.

FIG. 62 illustrates the second embodiment accessing data register 5.

FIG. 63 illustrates a data register 5 timing diagram of the secondembodiment.

FIG. 64 illustrates the use of a clock gating signal by the secondembodiment.

FIG. 65 illustrates a timing diagram of the second embodiment using thegating signal.

FIG. 66A illustrates data registers 3 and 5 placed in series between TDIand TDO.

FIG. 66B illustrates a timing diagram using the gating signal of thesecond embodiment.

FIG. 67 illustrates a parallel data register access architecture of thesecond embodiment.

FIG. 68A illustrates access to parallel data registers 1 by the secondembodiment.

FIG. 68B illustrates access to parallel data registers 2 by the secondembodiment.

FIG. 68C illustrates access to parallel data registers 3 by the secondembodiment.

FIG. 68D illustrates access to parallel data registers 4 by the secondembodiment.

FIG. 68E illustrates access to parallel data registers 5 by the secondembodiment.

FIG. 68F illustrates access to parallel data registers 3 and 5 by thesecond embodiment.

FIG. 69 illustrates a first test configuration according to the secondembodiment.

FIG. 70 illustrates a second test configuration according to the secondembodiment.

FIG. 71 illustrates a third test configuration according to the secondembodiment.

FIG. 72 illustrates a fourth test configuration according to the secondembodiment.

FIG. 73 illustrates a fifth test configuration according to the secondembodiment.

FIG. 74 illustrates a sixth test configuration according to the secondembodiment.

FIG. 75 illustrates a seventh test configuration according to the secondembodiment.

FIG. 76 illustrates a eighth test configuration according to the secondembodiment.

FIG. 77 illustrates a TAP+ATC domain linking architecture of the secondembodiment.

FIG. 78 illustrates input and output linking elements of the FIG. 77architecture.

FIG. 79 illustrates the TAP Linking Module (TLM) of FIG. 77architecture.

FIG. 80 illustrates different domain linkages during TAP instructionscans.

FIG. 81 illustrates different domain linkages during TAP data scans.

FIG. 82 illustrates each TAP+ATC domain having separate ATC buses.

FIG. 83 illustrates the second embodiment with a WSP for IEEE P1500compliance.

DETAILED DESCRIPTION

FIG. 47 illustrates a circuit 4702 which represents architecturalmodifications made to circuit 4602 according to the first embodiment.The modifications include the placement of a multiplexer 4704 in the WSPcontrol bus path to architecture 4610, the placement of a multiplexer4706 in the WSI input path to architecture 4610, the placement of amultiplexer 4708 in the TDO path from architecture 4604, and theaddition of a multiplexer control output signal 4710 on the instructionregister 314 bus 312 of architecture 4604. Multiplexer 4704 allows forthe instruction and data register control bus input 4718 to architecture4610 to selectively come from either the WSP 202 or the TAP 318.Multiplexer 4706 allows for the serial data input 4712 to architecture4610 to selectively come from either the WSI input on bus 4612 or theserial data output 4714 from architecture 4604. Multiplexer 4708 allowsfor the TDO output of bus 4608 to selectively come from either theserial data output 4714 of architecture 4604 or the serial data output4716 of architecture 4610. The control signal 4710 regulates theoperation of all multiplexers 4704-4708. The value of the control signal4710 is established by the instruction loaded into instruction register314 of architecture 4604.

When initialized by power up, resetting or by the loading of aninstruction that sets control signal 4710 low, the multiplexers4704-4708 in circuit 4702 are set to allow TAP 318 exclusive access ofarchitecture 4604 via TDI and TDO and WSP 202 exclusive access ofarchitecture 4610 via WSI and WSO. In this mode, the operation of theTAP based architecture 4604 and WSP based architecture 4610 is identicalto that described in circuit 4602 of FIG. 46.

When TAP access of architecture 4610 is desired, the TAP will load aninstruction into instruction register 314 of architecture 4604 that setscontrol signal 4710 high. In response, the multiplexers 4704-4708 willbe set such that; (1) instruction and data register control bus 4718 toarchitecture 4610 is coupled to the TAP 318 instruction and dataregister control bus instead of the WSP 202 instruction and dataregister control bus, (2) the serial data input 4712 of architecture4610 is coupled to the serial data output 4714 of architecture 4604instead of the WSI input of bus 4612, and (3) the serial data output4716 of architecture 4610 is coupled to the TDO output of bus 4608instead of the serial output 4714 of architecture 4604. In this mode,architectures 4604 and 4610 are placed in series with each other betweenTDI and TDO and receive common control input from TAP 318. During TAPcontrolled instruction scan operations the instruction registers 314 ofboth architectures are serially shifted from TDI to TDO to loadinstructions into architecture 4604 and architecture 4601. During TAPcontrolled data scan operations the selected data register in the set ofdata registers 316 of both architectures are serially shifted from TDIto TDO to load test data into the selected data registers ofarchitecture 4604 and architecture 4610.

FIG. 48 illustrates multiplexer 4704 in more detail. If the controlsignal 4710 is set low, multiplexer 4704 couples the WSP 202 instructionand data register control bus inputs to multiplexer input port A to themultiplexer instruction and data register control bus outputs onmultiplexer output port C 4718. If the control signal 4710 is set high,multiplexer 4704 couples the TAP 318 instruction and data registercontrol bus inputs to multiplexer input port B to the multiplexerinstruction and data register control bus outputs on output port C 4718.Thus by control of multiplexer 4704, the TAP can determine, by theloading of instructions in the instruction register 314 of architecture4604, whether the control for operating instruction and data registersin architecture 4610 comes from the WSP 202 or from the TAP 318. As seenin FIG. 48, the TAP has no equivalent control signal for the TransferDRoutput from the WSP. Therefore the TransferDR input to multiplexer inputport B can be wired to a fixed value (low) or wired to the Transferinput to the WSP, both possibilities being shown in dotted line.

If architecture 4610 does not include data registers with transfer cells(i.e. data register 5 types), the TransferDR input on input port B maybe wired to a fixed value, or deleted altogether along with theTransferDR output on output port C. If architecture 4610 includes dataregister 5 types, the TransferDR input to port B can be wired to theWSP's Transfer input. If wired to the WSP's Transfer input, it ispossible to control the TransferDR signal, via the Transfer input,during times when the TAP 318 is selected to access data register 5types and during times when the TAP is in the Shift-DR state.

These Shift-DR state times were previously indicated in timing diagramFIGS. 11, 13, 15, and 17 as dotted boxes beginning with A and endingwith B. To achieve Transfer operations when the TAP is accessing a dataregister 5 type and during the TAP Shift-DR state, a subtle modificationto the input multiplexer 4012 of transfer cell 4004 in FIG. 40 isrequired. This modification is shown in transfer cell 6204 of FIG. 62where it is seen by dotted box that the input multiplexer 6206 selectsthe transfer mode of operation whenever the Transfer-5 signal(TransferDR) is high, regardless of the state of the Shift-5 signal(ShiftDR).

The timing diagram of FIG. 63 indicates transfer operations taking placeby manipulation of the Transfer-5 input while the TAP is in the Shift-DRstate (Shift-5 high), as indicated by the A and B dotted line box. Bymentally substituting transfer cell 6204 for transfer cell 4004 and theTAP of FIG. 62 for the WSP of FIG. 40 it is clear that all the shift (S)and transfer (T) operation examples given in FIGS. 41-44 are operablefrom the timing diagram of FIG. 63.

From the above description it is seen that the first embodiment, asdepicted in the test architecture arrangement of circuit 4702 of FIG.47, provides the following improvements over the test architecturearrangement of circuit 4602 of FIG. 46.

-   -   1. The test architecture arrangement of circuit 4702, like the        test architecture arrangement of circuit 4602, allows for the        separate operation of the TAP based and WSP based test        architectures 4604 and 4610. Having separate operation of the        WSP 202 and its architecture 4610 allows compatibility with the        IEEE P1500 standard.    -   2. The test architecture arrangement of circuit 4702, unlike the        test architecture of circuit 4602, allows for serially linking        architectures 4604 and 4610 together and controlling the        serially linked architectures using TAP 318. Also the linking        and unlinking of the architectures 4604 and 4610 is controlled        by the TAP loading of instruction register 314 in architecture        4604. Thus the TAP 318 and its architecture 4604 has mastership        over the WSP 202 and its architecture 4610. Among other        benefits, this importantly allows test architecture 4610 to be        expandable into providing the previously described real time        operations (test, emulation, debug, etc.) currently enjoyed by        architecture 4604, which is made possible by the TAP's dedicated        test bus 4608 interface.    -   3. The test architecture arrangement of circuit 4702 allows,        while the architectures 4602 and 4702 are serially linked and        controlled by the TAP in the Shift-DR state, performing transfer        operations to data registers that include transfer cells. This        allows duplicating the transfer mode of operation introduced by        the IEEE P1500 standard using the TAP test bus and an additional        signal for enabling the Transfer operation.

A problem with the first embodiment is that it still requires both TAP318 and WSP 202 test interfaces and their associated architectures 4604and 4610 to be used in circuit 4702. Requiring both test interfaces andarchitectures increases test circuitry overhead in circuit 4702. Alsorequiring both architectures decreases instruction and data scanefficiency since, when the architectures are serially linked andcontrolled by the TAP, there is always two instruction registers toshift through from TDI to TDO during instruction scan operations and twodata registers to shift through from TDI to TDO during data scanoperations. Further, when the architectures 4604 and 4610 are seriallylinked and controlled by the TAP, it is not possible to perform theflexible and tightly timed IEEE P1500 WSP controlled capture, shift, andupdate operations on a data register as shown in FIGS. 28, 31, 34, 35,38, and 39. When under control of the TAP, the capture, shift, andupdate timing occurs in a regimented fashion according to TAP statediagram of FIG. 4.

FIG. 49 illustrates a circuit 4902 which represents architecturalmodifications to circuit 4602 according to the second embodiment. Themodifications include: (1) combining the architectures 4604 and 4610 ofcircuit 4602 to form a single merged architecture 4904, (2) eliminatingthe WSP 202 test interface of circuit 4602, and (3) adding an auxiliarytest control (ATC) bus of signals 4908 and combining those signals withthe TAP 318 test bus 4608 to form a merged test interface 4906 whichprovides control and access to the merged architecture 4904.

FIG. 50 illustrates the merged test interface 4906 and mergedarchitecture 4904 in more detail. As seen, the merged test interface4906 and architecture 4904 is identical to the TAP based architecture ofFIG. 2, with the exception that the merged architecture 4904 includes anadditional gating circuit 5004. The gating circuit 5004 receives input5006 from the data register control bus 304 from TAP 318, the ATC bus4908, and input 5010 from the instruction register 314. The gatingcircuit 5004 outputs signals 5008 to gating circuit 308.

FIG. 51 illustrates in further detail the merged test interface andarchitecture of FIGS. 49 and 50. The similarity to the TAP basedarchitecture of FIG. 3 is clearly apparent. The key difference being theaddition of the gating circuit 5004 and the ATC bus 4908. As will beseen in more detail later, gating circuit 5004 serves to interceptcertain ones of signals from the TAP's data register control bus 304 onbus 5006, gate the intercepted signals with signals input from the ATCbus 4908 (Capture, Update, and Transfer), and output the gated signalsto gating circuit 308 via bus 5008. The purpose of gating circuit 5004is to allow signals on the ATC bus 4908 to operate while the TAP is inthe Shift-DR state to perform the flexible and tightly timed capture,shift, update, and/or update operations that were achieved using theWSP.

The TAP 318 accesses the instruction register 314 in the same way asdescribed previously in regard to FIGS. 6-9. In the merged architecture4904, it is seen that a single instruction register 314 isadvantageously utilized instead having two separate instructionregisters in the non-merged architectures 4604 and 4610 of FIGS. 46 and47.

In preparation for the following description, it is good to revisit thedotted line box beginning with A and ending with B in timing diagramFIGS. 11, 13, 15, and 17. This A-B time frame indicates when the TAP isin its ShiftDR state. While in the ShiftDR state, the TAP continuouslyenables its ClockDR output to allow data to be transferred through thegated data register design examples of FIGS. 10 and 14. Likewise, whilein the ShiftDR state the TAP sets the ShiftDR state indication output onbus 304 high to allow data to be transferred in the synchronous dataregister design example of FIGS. 12 and 16. The second embodimentutilizes the TAP's ShiftDR state in combination with the ATC bus signals4908 to allow data registers to perform all the flexible and tightlytimed capture, shift, update, and/or transfer operations achieved by theWSP. All the flexible and tightly timed test operations, as describedbelow using the previous examples, will occur entirely within the A-Btime frame with the TAP in the ShiftDR state.

FIG. 52 illustrates the data register 1 example of FIG. 10 adapted toinclude the gating circuit 5004 and ATC bus 4908. As seen, gatingcircuit 5004 inputs, on bus 5006, the ShiftDR and UpdateDR signals fromTAP bus 304, the ATC bus signals 4908, and the ATC enable signal 5010from instruction register 314. The gating circuit 5004 outputs, on bus5008, gated versions of the ShiftDR and UpdateDR signals to gatingcircuit 308. If the TAP is to control scan operations to data register1, as previously described in FIGS. 10 and 11, the ATC enable signal5010 will be set low to disable the ATC bus signals 4908 from effectingthe TAP's mode of operation. However, if data register 1 is to becontrolled using the mode of operation of the second embodiment the ATCenable signal 5010 will be set high by an instruction scanned into theinstruction register to enable the ATC bus signals 4908.

When the ATC enable signal 5010 is high, gates 5202 and 5204 of gatingcircuit 5004 are enabled to allow the ATC Capture signal to directlycontrol the Shift-1 input of data register 1. Also gates 5206 and 5208of gating circuit 5004 are enabled to allow the ATC Update signal todirectly control the Update-1 input of data register 1. Since the ATCTransfer signal is not used in this example, it is simply shown as aninput to gating circuit 5004.

Recalling from FIGS. 10 and 11 that the TAP's ShiftDR output is highduring the ShiftDR state, it is clear that a logic one asserted onto theATC Capture signal will cause a logic low on the Shift-1 input of dataregister 1, causing scan cells 1004 in data register 1 to capture data.Also recalling from FIGS. 10 and 11 that the TAP's UpdateDR output islow during the ShiftDR state, it is clear that a clock pulse on the ATCUpdate signal will cause a clock pulse on the Update-1 input of dataregister 1, causing scan cells 1004 in data register 1 to update data.

FIG. 53 illustrates a timing example of the second embodiment wherebythe ATC Capture and Update signals of FIG. 52 are activated during anA-B time frame while the TAP is in the ShiftDR state to duplicate thetightly timed WSP capture and shift operations of FIG. 28. Clock-1 runscontinuously with the ClockDR output from the TAP during the ShiftDRstate.

FIG. 54 illustrates the data register 2 example of FIG. 12 adapted toinclude the gating circuit 5004 and ATC bus 4908. The scan cells 5404 indata register 2 are shown modified from the scan cells 1204 of FIG. 12to the extent that the input multiplexer 5406 is changed to cause acapture operation to occur whenever the Capture-2 input goes high. Thisis required since the Shift-2 input remains high by the TAP remaining inthe ShiftDR state when testing according to the second embodiment. Asseen, gating circuit 5004 inputs, on bus 5006, the CaptureDR state andthe UpdateDR signals from TAP bus 304, the ATC bus signals 4908, and theATC enable signal 5010 from instruction register 314.

The gating circuit 5004 outputs, on bus 5008, gated versions of theCaptureDR state and UpdateDR signals to gating circuit 308. If the TAPis to control scan operations to data register 2, as previouslydescribed in FIGS. 12 and 13, the ATC enable signal 5010 will be set lowto disable the ATC bus signals 4908 from effecting the TAP's mode ofoperation. However, if data register 1 is to be controlled using themode of operation of the second embodiment the ATC enable signal 5010will be set high by an instruction scanned into the instruction registerto enable the ATC bus signals.

When the ATC enable signal 5010 is high, gates 5402 and 5404 of gatingcircuit 5004 are enabled to allow the ATC Capture signal to directlycontrol the Capture-2 input of data register 2. Also gates 5206 and 5208of gating circuit 5004 are enabled to allow the ATC Update signal todirectly control the Update-2 input of data register 2. Recalling fromFIGS. 12 and 13 that the TAP's CaptureDR state signal is low during theShiftDR state, it is clear that a logic one asserted onto the ATCCapture signal will cause a logic one on the Capture-2 input of dataregister 2, causing scan cells 5404 in data register 2 to capture data.Also recalling from FIGS. 12 and 13 that the TAP's UpdateDR output islow during the ShiftDR state, it is clear that a clock pulse on the ATCUpdate signal will cause a clock pulse on the Update-2 input of dataregister 2, causing scan cells 5404 in data register 2 to update data.

FIG. 55 illustrates a timing example of the second embodiment wherebythe ATC Capture and Update signals of FIG. 54 are activated during anA-B time frame while the TAP is in the ShiftDR state to duplicate thetightly timed WSP capture, shift, and update operations of FIG. 31.While not shown, the Shift-2 signal is high during the A-B time framesince the TAP is in the ShiftDR state. Clock-2 runs continuously withTCK during test.

FIG. 56 illustrates the data register 3 example of FIG. 14 adapted toinclude the gating circuit 5004 and ATC bus 4908. As seen, gatingcircuit 5004 inputs, on bus 5006, the ShiftDR signal from TAP bus 304,the ATC bus signals 4908, and the ATC enable signal 5010 frominstruction register 314. The gating circuit 5004 outputs, on bus 5008,a gated version of the ShiftDR signal to gating circuit 308. If the TAPis to control scan operations to data register 3, as previouslydescribed in FIGS. 14 and 15, the ATC enable signal 5010 will be set lowto disable the ATC bus signals 4908 from effecting the TAP's mode ofoperation. However, if data register 3 is to be controlled using themode of operation of the second embodiment the ATC enable signal 5010will be set high by an instruction scanned into the instruction registerto enable the ATC bus signals.

When the ATC enable signal 5010 is high, gates 5202 and 5204 of gatingcircuit 5004 are enabled to allow the ATC Capture signal to directlycontrol the Shift-3 input of data register 3. Since the ATC Update andTransfer signals are not used they are shown simply as inputs to gatingcircuit 5004. Recalling from FIGS. 14 and 15 that the TAP's ShiftDRoutput is high during the ShiftDR state, it is clear that a logic oneasserted onto the ATC Capture signal will cause a logic low on theShift-3 input of data register 3, causing scan cells 1404 in dataregister 3 to capture data.

FIGS. 57 and 58 illustrate timing examples of the second embodimentwhereby the ATC Capture signal of FIG. 56 is activated during A-B timeframes while the TAP is in the ShiftDR state to duplicate the tightlytimed WSP capture and shift operations of FIGS. 34 and 35. Clock-3 runscontinuously with the ClockDR output from the TAP during the ShiftDRstate.

FIG. 59 illustrates the data register 4 example of FIG. 16 adapted toinclude the gating circuit 5004 and ATC bus 4908. The scan cells 5904 indata register 4 are shown modified from the scan cells 1604 of FIG. 16to the extent that the input multiplexer 5906 is changed to cause acapture operation to occur whenever the Capture-4 input goes high. Thisis required since the Shift-4 input remains high by the TAP remaining inthe ShiftDR state when testing according to the second embodiment. Asseen, gating circuit 5004 inputs, on bus 5006, the CaptureDR statesignal from TAP bus 304, the ATC bus signals 4908, and the ATC enablesignal 5010 from instruction register 314. The gating circuit 5004outputs, on bus 5008, gated versions of the CaptureDR state signal togating circuit 308.

If the TAP is to control scan operations to data register 4, aspreviously described in FIGS. 16 and 17, the ATC enable signal 5010 willbe set low to disable the ATC bus signals 4908 from effecting the TAP'smode of operation. However, if data register 4 is to be controlled usingthe mode of operation of the second embodiment the ATC enable signal5010 will be set high by an instruction scanned into the instructionregister to enable the ATC bus signals.

When the ATC enable signal 5010 is high, gates 5402 and 5404 of gatingcircuit 5004 are enabled to allow the ATC Capture signal to directlycontrol the Capture-4 input of data register 4. Recalling from FIGS. 16and 17 that the TAP's CaptureDR state signal is low during the ShiftDRstate, it is clear that a logic one asserted onto the ATC Capture signalwill cause a logic one on the Capture-4 input of data register 4,causing scan cells 5904 in data register 4 to capture data.

FIGS. 60 and 61 illustrate timing examples of the second embodimentwhereby the ATC Capture signal of FIG. 59 is activated during A-B timeframes while the TAP is in the ShiftDR state to duplicate the tightlytimed WSP capture and shift operations of FIGS. 38 and 39. While notshown, the Shift-4 signal is high during the A-B time frame since theTAP is in the ShiftDR state. Clock-4 runs continuously with the TCKduring the test.

FIG. 62 illustrates the data register 5 example of FIG. 40 adapted toinclude TAP 318 in place of WSP 202, the gating circuit 5004, and ATCbus 4908. As seen, gating circuit 5004 inputs the ATC bus signals 4908and the ATC enable signal 5010 from instruction register 314. Since TAP318 does not have an equivalent transfer signal to be gated with the ATCTransfer signal, no input bus 5006 is required. The gating circuit 5004outputs, on bus 5008, a Transfer signal to gating circuit 308.

When the ATC enable signal 5010 is set high by an instruction ininstruction register 314, gate 6202 of gating circuit 5004 is enabled toallow the ATC Transfer signal to directly control the Transfer-5 inputof data register 5. Since the ATC Capture and Update signals are notused they are shown simply as inputs to gating circuit 5004. During thetransfer test mode, the TAP is placed in the ShiftDR state to enable theClockDR output to drive the Clock-5 input and to set the ShiftDR outputhigh to set the Shift-5 input high. While the TAP is in the ShiftDRstate, the ATC Transfer signal can be manipulated to cause data register5 to perform shift (S) and transfer (T) operations as shown in timingdiagram of FIG. 63.

The TAP and ATC Transfer signal can therefore duplicate the WSP transfertest mode operation and timing shown in FIGS. 41-45. As previouslymentioned in regard to FIG. 48, the data register 5 transfer cells 6204of FIG. 62 are modified from the data register 5 transfer cells 4004 tothe extent that the input multiplexer 6206 selects transfer operations(T) whenever the Transfer-5 input is high, independent of the state ofthe Shift-5 input.

FIG. 64 illustrates that the ATC bus 4908 may include additional signalsin addition to the Capture, Update, and Transfer that may be requiredfor controlling a data register during test. FIG. 64 is the same as thepreviously described FIG. 56 with the exceptions that (1) the ATC busincludes a Gate signal, (2) gating circuit 5004 includes a gate 6402,and (3) gating circuit 308 includes a gate 6404. When ATC enable signal5010 is set high, data register 3 can be accessed and operated asdescribed in FIGS. 56, 57, and 58.

If during the operating it is desired to disable ClockDR from drivingthe Clock-3 input of data register 3, the ATC Gate signal is set highwhich causes gate 6402 to force the output of gate 6404 low. As seen inthe timing diagram of FIG. 65 all capture and shift operations of dataregister 3 are suspended while the ATC Gate input is high. While simplyturning off the TAP's TCK could be used to do the same thing, thefollowing example illustrates a test situation where it is required tokeep the TCK running to clock one data register while using the ATC Gateinput to gate off clocking of another data register.

FIG. 66A illustrates a configuration where data register 3 (1402) ofFIG. 64 is placed in series with data register 5 (4002) of FIG. 62between TDI and TDO. Gating circuit 308 of FIG. 64 is shown providingClock-3 and Shift-3 input to data register 3 (1402) and gating circuit308 of FIG. 62 is shown providing Clock-5, Shift-5, and Transfer-5 inputto data register 5 (4002). Both data registers are operated while theTAP is in the ShiftDR state according to the second embodiment aspreviously described.

In the timing diagram of FIG. 66B is it seen that data register 3operates to do a single capture (C) operation 6602 followed by asequence of shift (S) operations 6604 while data register 5 operates todo three transfer (T) operations 6606-6610 followed by a sequence ofshift (S) operations 6612. To insure that only one capture (C) operation6602 is performed by data register 3 and to insure that shifting (S)operations 6604 and 6612 of both registers are aligned and work properlyfrom TDI to TDO, the ATC Gate input of FIG. 64 is set high to gate offthe Clock-3 input to data register 3 during the second 6608 and third6610 transfer (T) operations of data register 5. As can be seen, withoutthe ATC Gate input it would not be possible to properly operate dataregisters 3 and 5 in their respective modes in the serial TDI to TDOarrangement of FIG. 66A.

Thus the importance of the ATC Gate input is that it allows for locallysuspending clocking operations on one data register while continuingclocking operations on another data register. While an ATC Gate input isshown providing this local clock suspension for the gated data register3 and 5 designs, other ATC input signal types could be provided tosuspend data register operations based on synchronous data registerdesigns that use scan cells with the ability to be placed in a holdingstate while being clocked, similar in nature to the scan cells 1204 and1604 of FIGS. 12 and 16 respectively.

FIG. 67 illustrates the test interface 4906 of the second embodimentused in combination with an architecture 6702 of the second embodiment.The architecture 6702 is the same as architecture 4904 of FIG. 50 withthe exception that architecture 6702 is designed to provide parallelaccess to data registers 1-N, in addition to the previously describedserial access of data registers 1-N. As seen, input multiplexers6704-6706 have been placed on the serial data inputs of data registers1-N to allow the serial data input of the data registers to be coupledto either the TDI input of test interface 4906 for serial access or to aseparate TDI 1-N inputs 6714-6716 to the architecture for parallelaccess.

Also, the serial data outputs of data registers 1-N are input to outputmultiplexers 6708-6710 for parallel access, in addition to being inputto the TDO multiplexer 6722 for serial access. The input and outputmultiplexers are controlled by a signal output 6712 from instructionregister 314. Instructions loaded into the instruction register controlthe output value of signal 6712.

During non-test modes, the TDI1-N inputs and TDO1-N outputs may used asfunctional input and output signals, as indicated by functional outputsshown being input to the output multiplexers 6708-6710. During testmodes, the TDI1-N inputs and TDO1-N outputs may be selected by signal6712 to become parallel inputs to and parallel outputs from dataregisters 1-N. Thus the architecture 6702 may operate to access a singledata register between TDI and TDO of test interface 4906 as previouslydescribed, or it may operate to access a parallel set of data registersbetween TDI1-N and TDO1-N.

If parallel TDI1-N to TDO1-N access of a set of data registers isselected, the operation can be controlled by the TAP alone or by the TAPin combination with the ATC bus signals 4908. Thus all the flexible andtightly timed capture, shift, update, and/or transfer operationspreviously described in regard to single data registers being accessedbetween TDI to TDO are possible when parallel data registers are beingaccessed between TDI1-N and TDO1-N.

FIGS. 68A-68E illustrate examples of parallel access of same type dataregisters 1 of FIG. 52, 2 of FIG. 54, 3 of FIG. 56, 4 or FIGS. 59, and 5of FIG. 62 between TDI1-N and TDO1-N. FIG. 68F illustrates parallelaccess of different type data registers 3 of FIG. 56 and 5 of FIG. 62between TDI1-N and TDO1-N. If alignment of the capture, transfer, andshifting operations of differing parallel data registers 3 and 5 isdesired, the ATC Gate signal can be used as previously described in theexamples of FIGS. 66A and 66B.

The following FIGS. 69-82 are provided to illustrate variousconfigurations of connecting core circuits residing in an IC thatinclude the TAP+ATC test domains of the second embodiment (i.e. theTAP+ATC test interface and architectures of FIGS. 50 and 67). Also shownis configuration examples of mixtures of core circuits that use thestandard TAP test domain (i.e. the TAP test interface and architectureof FIG. 1) and core circuits that use the TAP+ATC test domains of thesecond embodiment. In the configurations showing a mixture of TAPdomains and TAP+ATC domains, it is important to notice the testcompatibility between these domains.

FIG. 69 illustrates an example configuration of three core circuits inan IC, each having a TAP+ATC domain consisting of test interface 4906and architecture 4904 of FIG. 50 of the second embodiment. The coreTAP+ATC domains are serially connected in a serial path between TDI andTDO to allow all TAP+ATC domains to be serially accessed at the sametime for loading instruction and data. The core TAP+ATC domains mayoperate in the standard TAP domain (FIG. 1) mode to achieve testingaccording to the IEEE 1149.1 and other mentioned sister standards, or inthe TAP+ATC mode to achieve testing according the second embodiment.

As previously mentioned and described, the TAP+ATC domains can duplicateall the flexible and tightly timed test operations of the IEEE P1500standard. Thus the core circuits do not need to include the separateIEEE P1500 standard comprising the WSP 202 and architecture 4610 of FIG.46.

FIG. 70 illustrates an example configuration of three core circuits inan IC. Core circuits 1 and 3 have TAP+ATC domains consisting of the testinterface 4906 and architecture 4904 of FIG. 49 of the secondembodiment. Core circuit 2 has the IEEE 1149.1 standard TAP domainconsisting of test interface 104 and architecture 102 of FIG. 1. Thecore TAP and TAP+ATC domains are serially connected in a serial pathbetween TDI and TDO to allow all domains to be serially accessed at thesame time for loading instruction and data. All cores can operate in thestandard TAP domain mode of FIG. 1 to achieve testing according to IEEE1149.1.

Cores 1 and 3 can additionally operate in the TAP+ATC domain mode toachieve testing according to the second embodiment. Since testingaccording to the second embodiment occurs while the TAP is in theShiftDR state, i.e. within the A-B time frames of FIGS. 53, 55, 57, 58,60, 61, 63, 65, and 66B, the TAP domain of core 2 may participate withthe TAP+ATC domain testing of cores 1 and 3 by simply shifting datathrough a selected data register during the ShiftDR state. DuringTAP+ATC testing of cores 1 and 3, the selected data register in the TAPdomain of core 2 serves simply as shifting path connection between theselected data register output of core 1 and the selected data registerinput of core 3.

Since all the flexible and tightly timed capture, shift, update, and/ortransfer operations occur by manipulation of the ATC bus inputs to cores1 and 3, and while the TAPs of cores 1-3 are in the ShiftDR state, thepresence of the data register of core 2 in the overall TDI to TDO serialpath of the cores is transparent to the testing.

FIG. 71 illustrates an example configuration of the TAP domain of FIG. 1serially connected to two TAP+ATC domains of FIG. 50. The TAP domain isthe host IC's IEEE 1149.1 standard TAP domain. The TAP+ATC domainsreside in cores 1 and 2 within the host IC. The IC's TAP domain andcore's TAP+ATC domains are serially connected in a serial path betweenTDI and TDO to allow all domains to be serially accessed at the sametime for loading instruction and data. All domains can operate in theTAP domain mode to achieve testing according to IEEE 1149.1. The domainsof cores 1 and 2 can additionally operate in the TAP+ATC domain mode toachieve testing according to the second embodiment.

Again, as in the FIG. 70 example, since testing according to the secondembodiment occurs while the TAP is in the ShiftDR state, the host IC'sTAP domain may participate with the TAP+ATC testing of cores 1 and 2 tothe extent that it serves to shift data from TDI to the serial input ofcore 1 during the ShiftDR state while the ATC bus signals of cores 1 and2 are manipulated to perform the flexible and tightly timed capture,shift, update, and/or transfer operations previously described.

FIG. 72 illustrates an example configuration of three core circuits inan IC, each having the TAP+ATC domain of FIG. 67 consisting of testinterface 4906 and architecture 6702. The TAP+ATC domains are seriallyconnected in a serial path between TDI and TDO to allow all domains tobe serially accessed at the same time for loading instruction and data.As described in FIG. 67, the data registers of architecture 6702 can beaccessed individually via the TDI to TDO serial path or in parallelusing each domain's parallel TDI1-N inputs and parallel TDO1-N outputs.

In FIG. 72, instructions have been loaded into the instruction registersof each TAP+ATC domain to allow data registers to be accessed via theTDI1-N inputs and TDO1-N output of each core. Once so configured, any ofthe previously described flexible and tightly timed parallel testoperations may be applied to each core using the TAP+ATC interfaces4906. The TAP+ATC domains of each core 1-3 are also operable byinstructions loaded into the instruction register to operate in theserial TDI to TDO test mode using either the serial TAP mode ofoperation of IEEE 1149.1 or the serial TAP+ATC mode of operation of thesecond embodiment.

FIG. 73 illustrates an alternate connection example of the three corecircuits of FIG. 72 whereby the parallel TDI1-N inputs and TDO1-Noutputs of each TAP+ATC domain are connected in series to form a serialconnection from the TDI1-N input of the core 1 domain to the TDO1-Noutput of the core 3 domain. Again, any of the flexible and tightlytimed test operations of the second embodiment may occur in each domainduring an A-B time frame using the TAP+ATC interfaces 4906.

FIG. 74 illustrates an example configuration of three core circuits inan IC. Core circuits 1 and 3 have TAP+ATC domains consisting of testinterface 4906 and architecture 6702 of the second embodiment. Corecircuit 2 has the IEEE 1149.1 standard TAP test interface 104 of FIG. 1,but the architecture 102 of FIG. 1 has been replaced in core 2 with theparallel TDI1-N input and TDO1-N output capable architecture 6702 ofFIG. 67. The core TAP and TAP+ATC domains are serially connected in aserial path between TDI and TDO to allow all domains to be seriallyaccessed at the same time for loading instruction and data.

Testing of the cores via the serial TDI to TDO path can occur usingeither the TAP or TAP+ATC modes described previously in regard to FIG.70. Like FIG. 73, the TAP and TAP+ATC domains are also seriallyconnected together via the parallel TDI1-N and TDO1-N bus. All cores canoperate in the standard TAP domain mode using the parallel TDI1-N toTDO1-N bussing path. Cores 1 and 3 can additionally operate in theTAP+ATC domain mode using the parallel TDI1-N to TDO1-N bussing path ofthe second embodiment. Since testing according to the second embodimentoccurs while the TAP is in the ShiftDR state, i.e. within the A-B timeframe, the TAP domain of core 2 may participate with the TAP+ATC domaintesting of cores 1 and 3 by simply shifting data through a selected setof data registers when testing occurs via the parallel TDI1-N to TDO1-Nbussing path.

During TAP+ATC testing of cores 1 and 3, the selected data registers inthe TAP domain of core 2 serve simply as shifting path connectionsbetween the selected data register outputs of core 1 and the selecteddata register inputs of core 3. Since all the flexible and tightly timedcapture, shift, update, and/or transfer operations occur by manipulationof the ATC bus inputs to cores 1 and 3, and while the TAPs of cores 1-3are in the ShiftDR state, the presence of the data registers of core 2in the overall TDI1-N to TDO1-N bussing path of the cores is transparentto the testing.

FIG. 75 illustrates an example configuration of three core circuits inan IC. Cores 1 and 3 have TAP+ATC domains consisting of test interface4906 and architecture 6702, and core 2 has a TAP+ATC domain consistingof test interface 4906 and architecture 4904. FIG. 75 is provided toindicate that it is possible to execute simultaneously both a paralleltest via TDI1-N to TDO1-N on cores 1 and/or 3 and a serial test via TDIto TDO on core 2. The data flow path of the parallel test is indicatedby dotted line 7504 and the data flow path of the serial test isindicated by dotted line 7502. As seen, the bypass data registers (BPR)of cores 1 and 3 are selected to be in series with the selected dataregister of core 2 during the serial TDI to TDO testing, to provide anabbreviate shifting path through cores 1 and 3.

During simultaneous serial and parallel testing, the TAPs of testinterfaces 4906 are placed in the ShiftDR state and the ATC bus signalsare manipulated to operate any of the flexible and tightly timedcapture, shift, update, and/or transfer operations the test requires.During the test, the BPRs of cores 1 and 3 remain in the shift data modesince the TAP remains in the ShiftDR state. The data registersperforming the test, other than the BPR, respond to the ATC bus signalswhile the TAP is in the ShiftDR state.

Assuming in the example of FIG. 75 that; (1) the bit length through theTDI1-N to TDO1-N parallel path of core 1 is 100 bits, (2) the length ofthe TDI to TDO serial path through cores 1, 2 and 3 is 1000 bits, (3)the bit length of the TDI1-N and TDO1-N parallel path through core 3 is500 bits, (4) the test operations of each path are controlled during theTAP ShiftDR state by a common ATC bus 4908, and (5) the testing of eachpath comprises the capture and shift operations of FIG. 57, thefollowing problem can be seen. When the ATC bus activates the capturesignal, all data register in the paths perform a capture operation.Following the capture operation all data registers in the paths resumetheir shifting operation to unload the captured data and load new testdata.

Since the TDI to TDO serial path must be unloaded and loaded followingeach capture operation, it establishes the length of the shift operationfor all paths at 1000 bits. Even though the parallel paths through cores1 and 3 could complete their unload and load operations in 100 and 500bit shifts respectively, they must operate in the shift mode for theentire 1000 bit shift to accommodate the unload and load of the TDI toTDO serial path. Thus the shifting time of the lesser length parallelpaths are forced to be equal to the shifting time of the longer lengthserial path.

If the test patterns of each core require the same number of shiftunload/load operations, the test time of cores 1 and 3 will be extendedto equal the test time of core 2. If cores 1 and 3 have additional teststhat must be performed, those additional tests are forced to be delayeduntil after the testing of core 2.

FIG. 76 illustrates a way of using the second embodiment to avoid thetesting delay described above. FIG. 76 is the same as FIG. 75 with theexception that each core is provided with a separate ATC bus. Core 1 isprovided with ATC-1 bus 7602, core 2 is provide with ATC-2 bus 7604, andcore 3 is provided with ATC-3 bus 7608. The cores are all loaded withtest instructions to select their data registers and to initiate theirtesting. Following the instruction load, the TAPs of the cores are setto the ShiftDR state to enable control input from ATC-1, ATC-2, andATC-3 to operate the capture and shift operations of cores 1, 2, and 3respectively.

During testing of core 1, the capture input of the ATC-1 bus isactivated to capture data into the 100 bit parallel TDI1-N to TDO1-Npath of core 1, then is deactivated to allow the 100 bit parallel pathto perform a 100 bit shift to unload and load data. The BPR of core 1 isdesigned to not be effected by the operation of the ATC-1 capture inputand remains in the shift data mode since the TAP is in the ShiftDR. ThisATC-1 bus controlled capture and shift process continues until all thetest data patterns have been applied to core 1.

During testing of core 2, the capture input of the ATC-2 bus isactivated to capture data into the data register of core 2 of the 1000bit serial TDI to TDO path through cores 1-3, then is deactivated toallow the 1000 bit serial path to perform a 1000 bit shift to unload andload data. The BPRs in core 1 and 3 of the 1000 bit serial TDI to TDOpath remain in shift data mode when the data register of core 2 performsa capture operation since the TAPs of core 1 and 3 are in the ShiftDRstate. This ATC-2 bus controlled capture and shift process continuesuntil all the test data patterns have been applied to core 2.

During testing of core 3, the capture input of the ATC-3 bus isactivated to capture data into the 500 bit parallel TDI1-N to TDO1-Npath of core 3 then is deactivated to allow the 500 bit parallel path toperform a 500 bit shift to unload and load data. The BPR of core 3 isdesigned to not be effected by the operation of the ATC-3 capture inputand remains in the shift data mode since the TAP is in the ShiftDRstate. This ATC-3 bus controlled capture and shift process continuesuntil all the test data patterns have been applied to core 3.

From the above description it is seen that by using separate ATC-1,ATC-2, and ATC-3 buses the testing of cores 1 and 3 can proceedindependent of each other and of core 2 and with capture and shiftoperation cycles optimized for their parallel path lengths of 100 and500 bits, respectively. Assuming the number test patterns applied toeach core is the same, the testing of core 1 occurs in one tenth thetest time of core 2, and the testing of core 3 occurs in one half thetest time of core 2. If cores 1 and 3 had additional tests to execute,those additional tests could be started and ran while the testing ofcore 2 continues. Thus the overall test time of the IC containing cores1-3 could be reduced, along with the associated test costs.

If a second ATC-1 operated test is required for say core 1, the TAPs ofcores 1-3 are transitioned out of the ShiftDR state following thecompletion of the first ATC-1 operated core 1 test to allow the TAPs tobe accessed to load the second test instruction into core 1 and toreload the current test instructions back into cores 2 and 3. Since theTAPs transition out of the ShiftDR state during the instruction loadoperation, the testing of cores 2 and 3 will be suspended. However,after instruction load operation, the TAPs of cores 1-3 can be onceagain set to the ShiftDR state where the second test of core 1 startsand the existing tests of cores 2 and 3 resume, all under control oftheir respective ATC-1, ATC-2 and ATC-3 buses.

While the use of separate ATC buses in FIG. 76 has been described asthey would be used in the core domain configuration of FIG. 75, separateATC buses can be used with any core domain configuration, such as coredomain configurations of FIGS. 69-74.

The example domain configurations of FIG. 69-75 show arrangements whereall domains reside in series between TDI and TDO. The following Figuresand description illustrate how TAP+ATC domains may be organized withinan IC to allow the domains to be selected individually, in desiredgroups, or all together between TDI and TDO. The following descriptionis based on a TAP Linking Architecture described in pending US patentpublication US 2001/0037479 A1, which is incorporated herein byreference.

While detail information about this architecture is provided in the USpatent publication, a sufficient description is provided below toillustrated how the architecture can be adapted to allow use of theTAP+ATC test interface 4906 of the second embodiment.

FIG. 77 illustrates a TAP linking architecture 7700 of the abovereferenced patent publication. The architecture is modified from thatdescribed in the patent publication to the extent that core domains7704-7706 and the IC domain 7702 have the TAP+ATC test interface 4906 ofthe second embodiment, instead of only the TAP test interface 318. Alsoan ATC bus 7708 is added to provide ATC bus signals to each domain'sTAP+ATC test interface. As described in the reference patentpublication, the architecture includes input linking circuitry 7710,output linking circuitry 7712, and a Tap Linking Module (TLM) circuit7714.

These architectural circuit elements operate together to allow any oneor more of the domains 7702-7706 to be linked between the ICs TDI input7716 and TDO output 7718 terminals and be controlled via the IC's TMS,TCK, and TRST input terminals. Following power up of the IC containingthe architecture 7700, the IC TAP+ATC domain 7702 will be the onlydomain between TDI 7716 and TDO 7718. This is required for compliancewith IEEE standard 1149.1 and described in the patent publicationreference.

FIG. 78 illustrates in more detail the TMS enable circuitry 7802 and theTDI input multiplexing circuitry 7804 that resides within the inputlinking circuitry 7710. The TDO output multiplexing circuitry 7806resides in the output linking circuitry 7700. The control for the TMSenable circuitry 7802, TDI input multiplexing circuitry 7804, and TDOoutput multiplexing circuitry 7806 comes from the TAP Linking Controloutput bus 7724 of TLM 7714.

FIG. 79 illustrates in more detail the TLM circuit 7714. The TLM has aTAP controller 318, an instruction register 7902, and multiplexer 7904.During TAP instruction scan operations, multiplexer 7904 is set to allowthe TLM to shift data through the instruction register 7902 from TDI7724 to TDO 7718. Instruction scans are used to input instructions toestablish link control signals on TAP Linking Control bus 7724. DuringTAP data scan operations, multiplexer 7902 is set to allow the TLM topass data from the TDI 7724 input to the TDO 7718 output.

FIG. 80 illustrates possible TAP+ATC domain configurations 8002-8014between TDI 7716 and TDO 7718 during instruction scan operations. Notethat the instruction register 7902 of the TLM 7714 is in the serial pathbetween TDI 7716 and TDO 7718 during instruction scan operations.Example TLM instruction codes 000-110 are a shown as codes selectingeach of the TAP+ATC domain configurations 8002-8014.

FIG. 81 illustrates possible TAP+ATC domain configurations 8102-8114between TDI 7716 and TDO 7718 during data scan operations. Note thatdata simply passes through the TLM in the serial path between TDI 7716and TDO 7718 during data scan operations. Since the TLM instructionregister is not accessed during data scan operations, the instructioncodes 000-110 for each TAP+ATC domain configuration 8002-8014 remainunchanged during data scan operation.

As can be seen from the above description, the TAP+ATC test interface ofthe second embodiment can easily be used in the TAP Linking Architectureof the referenced patent publication. Indeed, when any of the TAP+ATCdomain configurations of FIGS. 80 and 81 are established, the TAPs ofthose domains may be placed in the ShiftDR state to allow the ATC bussignals to be manipulated to achieve any of the flexible and tightlytimed capture, shift, update, and/or transfer operations previouslydescribed.

FIG. 82 is provided to indicate that each TAP+ATC domain may have itsown ATC bus (ATC_(IC) for the IC domain, ATC_(C1) for the core 1 domain,and ATC_(CN) for the core N domain) to allow for the test time reductionadvantages described previously in regard to FIG. 76.

FIG. 83 illustrates the optional use of the IEEE P1500 WSP in theTAP+ATC block diagram architecture of the second embodiment. Includingthe WSP may be desired to be compliant with the IEEE P1500 standard testinterface 1804. As seen, the TAP+ATC with WSP architecture is similar tothat of FIG. 51 with the exceptions that it includes the WSP 202,multiplexers 8302-8306, WSI and WSO input and output 8318, and a WSPENAinput 8322.

When the architecture of FIG. 83 is to operate using the TAP+ATC testinterface as previously described, the WSPENA input will be set low. Alow on WSPENA 8322 will cause; (1) multiplexer 8302 to couple inputbuses 304T (T indicates the TAP's 304 bus) and 5008 to gating circuit308 via bus 8310, (2) multiplexer 8304 to couple input bus 302T toinstruction register 314 via bus 8308, (3) multiplexer 8306 to couplethe TAP's Select and Reset outputs 8312 (FIG. 50) to the Select andReset outputs 8316, allowing the TAP to control reset operations andselection of data or instruction register scans. Thus, when WSPENA islow, the architecture of FIG. 83 is configured to operate as the TAP+ATCbased architecture of FIG. 51 and in all the modes described.

When the architecture of FIG. 83 is to operate using the WSP testinterface as previously described, the WSPENA input will be set high. Ahigh on WSPENA 8322 will cause; (1) multiplexer 8302 to couple input bus304W (W indicates the WSP's 304 bus) to gating circuit 308 via bus 8310,(2) multiplexer 8304 to couple input bus 302W to instruction register314 via bus 8308, (3) multiplexer 8306 to couple the WSP's Select andReset outputs 8312 (FIG. 10) to the Select and Reset outputs 8316,allowing the WSP to control reset operations and selection of data orinstruction register scans.

Also when WSPENA is high, the serial input (TDI/WSI) and output(TDO/WSO) of the instruction 314 and data registers 316 can be operatedfrom the WSI and WSO 8318 of the WSP test interface 1804. The Capture,Update, and Transfer signals of the ATC bus 4908 are input to the WSPalong with the additionally required and added WSP signals Shift,Select, Reset, and Clock 8320. Thus, when WSPENA is high, thearchitecture of FIG. 83 is configured to operate as the WSP basedarchitecture of FIG. 20 and in all the modes described.

While the second embodiment has been shown allowing TAP 318 based IC andcore designs to be augmented with ATC bus signals to enable the flexibleand tightly timed test operations of the IEEE P1500 WSP test interface202, the ATC bus signals are not limited to only signal types forduplicating IEEE P1500 operations. Indeed, the ATC bus may include othersignal types to allow the second embodiment to be used to perform otheroperations related to improvements in testing, emulation, debug, and insystem programming. In a broad sense, the second embodiment introducesthe opportunity of performing any desired operation by manipulation ofone of more signals on the ATC bus while the TAP is in its ShiftDRstate.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade herein without departing from the spirit and scope of the inventionas defined by the appended claims.

1. A circuit comprising: A. test access port having: i. a TDI lead, aTDO lead, a TMS lead, a TCK lead, and a TRST lead; and ii. a test accessport controller having inputs connected to the TMS, TCK and TRST leadsand having ClockIR, ShiftIR, CaptureIR, UpdateIR, Reset, Select,ClockDR, ShiftDR, CaptureDR, and UpdateDR output leads; B. a wrapperserial port having: i. a clock lead, a capture lead, a shift lead, anupdate lead, a transfer lead, a reset lead, a select lead, a WSI lead,and a WSO lead; and ii. a wrapper serial port controller having inputsconnected to the clock lead, the capture lead, the shift lead, theupdate lead, the transfer lead, the reset lead, and the select lead, andhaving ClockIR, ShiftIR, CaptureIR, UpdateIR, Reset, Select, ClockDR,ShiftDR, CaptureDR, UpdateDR, and TransferDR output leads; and C.multiplexer circuitry having a first bus input connected to the outputleads of the test access port controller and having a TransferDR input,a second bus input connected to the output leads of the wrapper serialport controller, and having an output bus having ClockIR, ShiftIR,CaptureIR, UpdateIR, Reset, Select, ClockDR, ShiftDR, CaptureDR,UpdateDR and TransferDR output leads.
 2. The circuit of claim 1 in whichthe TransferDR input of the first bus input is connected to a fixedvoltage.
 3. The circuit of claim 1 in which the TransferDR input of thefirst bus input is connected to the transfer lead of the wrapper serialport.